This book focuses primarily on the most efficient way to make an accurate FNA diagnosis of metastatic tumors within the broad confines of cytopathology. The text provides a step-by-step “thought process” during the diagnostic approach of the metastatic tumors using detailed algorithms. Starting from the onsite immediate FNA sample assessment, the book provides strategy of specimen triage to facilitate further cytology evaluation based on the metastatic patterns and morphologic patterns of the tumors. In the subsequent chapter, the book provides tips and traps of selecting markers and interpretation of immunoperoxidase, flow cytometric, cytogenetic and molecular studies. The book includes the strategy of dealing with limited FNA material and wisely use existing samples (cell block, direct smear, cytospin) for different ancillary studies including molecular tests that have been used at MD Anderson. The author highlights challenging issues to show the importance of using a multidisciplinary (clinical, radiologic, cytologic and ancillary studies) approach. Extensive illustrations are provided.